#include <stdio.h>
#include <string.h>
#include<unistd.h>
int main()
{
        const char *msg0="hello printf\n";
        const char *msg1="hello fwrite\n";
        const char *msg2="hello write\n";
        printf("%s", msg0);
        fwrite(msg1, strlen(msg0), 1, stdout);

        // system interface
        write(1, msg2, strlen(msg2));
        fork();
        return 0;
}
